Conventionally, laminates such as adhesive tapes, adhesive sheets and the like are widely used for adhesion to various surfaces to be adhered to such as metal, glass, lumber, paper, cardboard, plastic and the like. For example, external pharmaceutical preparations can be mentioned, wherein a drug is transdermally administered from the skin surface by adhering, to the skin, an adhesive sheet comprising a pressure-sensitive adhesive layer comprising a drug and laminated on a support such as plastic film, non-woven fabric, woven fabric, foil, composite films thereof and the like. As an adhesive constituting a pressure-sensitive adhesive layer, various kinds of polymer substances are used. In view of the adhesiveness and various chemical properties, a number of acrylic adhesives containing an acrylic copolymer have been widely used (JP-B-03-39485, JP-A-03-112558 and JP-A-03-127725).
The advantages of the acrylic adhesives are that various properties can be expressed by changing the composition of copolymer, and the solubility of drug and compatibility of additive can be designed to a certain extent. In addition, introduction of a functional group into a copolymer forms a chemical crosslinking point, and a crosslinking treatment can markedly increase the amounts of the pharmaceutical agent and additives to be added.